The present invention generally relates to magnetically-driven pumps. More particularly, the present invention relates to pumps adapted for pumping highly corrosive liquids.
Pumps for corrosive agents are especially employed in the chemical industry. In such pumps wherein a magnetic rotor is employed, it is necessary to bear the rotatory unit (composed of the magnetic rotor, the pump shaft and the impeller) both radially as well as axially in a pump housing.
Previously, in magnetic pumps for highly corrosive agents, it has been conventional to manufacture the pump shaft of steel with a plastic cladding for protection against the aggressive agents. The impeller and magnetic rotor also typically have injected clad metal bushes for transmitting the torque. These must be sealed from the aggressive agents with seal elements in an involved way.
The German periodical CAV, September 1982, pages 58 and 59, discloses a magnetic pump wherein a pump shaft is made of metal and is seated in plain bearing bushes via a hard ceramic sleeve. An impeller bush and a magnetic rotor bush of hard ceramic have only an axial bearing function and contribute nothing to the transmission of torque between the pump shaft and the magnetic rotor or, respectively, impeller. On the contrary, a corresponding, torsional connection of the metal parts of the magnetic rotor, pump shaft and impeller is provided with respect thereto. The corresponding metal parts must be reliably protected by appropriate seals against the aggressive agents to be pumped, resulting in a considerable plurality of required component parts.
The German periodical CAV, April 1993, pages 64 and 86, discloses a pump having a magnetic clutch wherein pump shaft is composed entirely of ceramic. Non-ceramic elements are also required here for the transmission of the torque between magnetic rotor, pump shaft and impeller.
Therefore, an object of the present invention is to provide an improved magnetic pump having a simple structure.
Another object of the present invention is to provide a .magnetic pump having improved resistance to corrosion from aggressive agents.